Modulus of elasticity or Young's modulus is the ratio of stress to strain. Within the elastic range below the
proportional limit, this ratio is a constant for a given piece of wood, making it useful in static bending tests
for determining the relative stiffness of a board. The modulus of elasticity is normally measured in pounds
per square inch (psi) and is abbreviated as MOE or E. Values for E relating to wood properties are commonly
in terms of million psi; for simplicity, a board with a modulus of elasticity of 2,100,000 psi. (2.1 x 106) may be
reported as 2.1E.